Guiding catheters are commonly used during coronary angioplasty procedures for delivering a balloon catheter to a treatment site in a coronary vessel. To move a guiding catheter safely through the vascular system and into the delicate coronary vessels, the guiding catheter must have a soft distal tip. The soft distal tip minimizes the risk of causing trauma to a vessel, freeing plaque from a vessel wall, puncturing a vessel, or creating embolisms in the bloodstream.
One nonanalogous, nonbraided angiographic catheter comprises an inner tube of polyamide externally tapered about the distal end and jacketed by a urethane material. The urethane material is internally tapered to match the externally tapered inner tube and extends beyond the distal end of the inner tube to form a flexible tip. Although well-suited as an angiographic catheter to withstand high burst pressures of injected contrast medium, the thickness of the catheter walls severely limits the use of this catheter as a guiding catheter through which an angioplasty balloon catheter is commonly inserted. The lumen of a guiding catheter must be as large as possible with a correspondingly thin catheter wall that can be pushed and guided through tortuous coronary vessels without causing trauma thereto.
One guiding catheter includes a wire-braided Teflon material inner tube with a polyurethane jacket epoxied thereto that abruptly terminates near the distal end of the inner tube. A metal radiopaque marker and a soft polyurethane tip are positioned around the distal end of the Teflon material inner tube and abut the abrupt, step-like shoulder at the distal end of the polyurethane jacket. The polyurethane tip is thermally bonded to the polyurethane jacket. A problem with this design is that the contact surface area between the abrupt, step-like shoulder of the polyurethane jacket and the proximal end of the polyurethane tip is limited, thereby significantly increasing the likelihood that the tip will be dislodged or separated from the step-like shoulder of the jacket. The metal radiopaque marker positioned between the jacket and tip further reduces the contact surface area therebetween and increases the likelihood of jacket and tip separation.